The present invention relates to a perpendicular magnetic recording medium that is mounted onto various magnetic recording devices and a manufacturing method for the same.
Instead of the longitudinal magnetic recording system of the prior art, a perpendicular magnetic recording system has been gathering attention as a technique for increasing densities of magnetic recordings. A perpendicular magnetic recording medium is constructed from a magnetic recording layer of a hard magnetic material and a backing layer of a soft magnetic material. The backing layer has the function of concentrating the magnetic flux that is generated by the magnetic head that is used in recording to the recording layer. Among the noises that are of concern in a perpendicular recording medium with this structure, spike noise is known to be a result of a magnetic domain wall formed in the soft magnetic layer that is the backing layer. As a result, in order to have reduced noise in the perpendicular magnetic recording medium, there is a need to prevent the magnetic domain wall formation in the soft magnetic layer.
As shown in Japanese Laid Open Patent Publication Number 6-180834 and Japanese Laid Open Patent Publication Number 10-214719 for example, a method is proposed for controlling the magnetic domain wall of this soft magnetic layer, wherein a ferromagnetic layer of a Co alloy or the like is formed as a top layer or bottom layer of the soft magnetic layer. The ferromagnetic layer is magnetized in the desired direction. Another proposed method forms an anti-ferromagnetic thin film. The exchange coupling fixes the magnetization of the soft magnetic layer.
With the method that uses an anti-ferromagnetic layer and controls the magnetic domain wall by exchange coupling with the soft magnetic layer, when adequate exchange coupling is achieved, the magnetic domain wall formation of the soft magnetic layer is prevented and is extremely effective. However, as indicated in Japanese Laid-open Patent Publication Number 10-214719 for example, in order to have adequate exchange coupling, after forming the film, heat treatment is necessary. This is extremely disadvantageous for mass production.
The object of the present invention is to provide a perpendicular magnetic recording medium having an anti-ferromagnetic layer that prevents magnetic domain wall formation of the soft magnetic layer. A further object of the present invention is to provide a manufacturing method for this perpendicular magnetic recording medium whereby mass production is conducted easily.
Intensive study was conducted on how to control the magnetic domain wall of the soft magnetic layer effectively by using an anti-ferromagnetic layer and on how to have a process design suitable for mass production. As a result, for the anti-ferromagnetic layer that is formed between the non-magnetic substrate and soft magnetic layer, the use of an Mn alloy containing at least Co at 10 atomic % or greater and 50 atomic % or less, or the use of an Mn alloy containing at least Ir at 10 atomic % or greater and 50 atomic % or less was discovered to be effective. Furthermore, it was determined that additional effectiveness could be obtained using an amorphous Co alloy as the soft magnetic layer.
When manufacturing this magnetic recording medium, a magnetic field of 796 A/m (10 Oe) or greater is applied in the radial direction of the substrate during the film formation of at least the anti-ferromagnetic layer and the soft magnetic layer. This produces a suitable amount of exchange coupling without requiring heat treatment or the like after film formation. The domain walls of the soft magnetic layer is effectively controlled.
The above, and other objects, features, and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.